Sandwich-like NiCo-LDH/rGO with rich mesopores and high charge transfer capability for flexible supercapacitors

Abstract

Layered double metal hydroxides (LDHs) have been widely used in the energy storage field due to their adjustable composition and interlayer spacing. However, easy agglomeration, poor electrical conductivity, and large volume changes during charge/discharge inhibit the application of LDH materials in the direction of supercapacitors. Herein, a sandwich-like NiCo-LDH/rGO composite is designed and prepared by a facile precipitation method, in which NiCo-LDHs grow vertically and uniformly on both sides of rGO. The novel sandwich structure of NiCo-LDH/rGO inhibits the agglomeration of NiCo-LDHs. And the interlaminar voids of NiCo-LDHs lead to the mesoporous morphology of the composites, which can alleviate the volume change stress during phase transition. Moreover, the work function difference between NiCo-LDHs and rGO causes the rapid charge transfer on the interface of NiCo-LDH/rGO composites. The electrochemical performance tests show that the as-prepared NiCo-LDH/rGO has a high specific capacity (2026.8 F g⁻¹ at 1 A g⁻¹ and 1425.6 F g⁻¹ at 30 A g⁻¹) and excellent cycling stability. The assembled flexible capacitor (NiCo-LDH/rGO//YP-50) exhibits a high energy density (52.0 W h kg⁻¹ at a power density of 800 W kg⁻¹) and outstanding cycle life (70% specific capacitance retention after 20 000 cycles). Our work designs a high energy density flexible supercapacitor by constructing a vertically grown LDH multistage structure on carbon materials, which provides new insight into the wearable energy storage field.